Miscellaneous: UPSC Previous Year Questions (Science and Technology)

Explanation

Green hydrogen is expected to play a prominent role in decarbonising heavy industries, including oil refineries, steel mills and fertiliser plants. Green hydrogen is produced by breaking down water in an electrolyser using only renewable energy, resulting in no carbon emissions. The production of fertiliser demands substantial energy, typically sourced from fossil fuels like natural gas. However, green hydrogen offers a promising alternative, serving either as an electricity source or directly utilised in the ammonia production process, which is crucial for manufacturing fertilizer. Oil refineries significantly contribute to greenhouse gas emissions through their energy-intensive operations and dependence on fossil fuels. However, integrating green hydrogen into refinery operations offers a viable solution to mitigate this impact by either substituting or complementing fossil fuels, thereby decreasing their carbon footprint. Hydrogen can play a vital role in refining procedures like hydrocracking and hydrotreating, enhancing fuel quality by eliminating impurities. The steel industry contributes substantially to worldwide carbon emissions. However, the adoption of green hydrogen presents an opportunity to address this issue by serving as a replacement for coal or coke as a reducing agent in the steelmaking process. Green hydrogen enables the Direct Reduced Iron (DRI) process, producing environmental -friendly or low-carbon steel. It can also support heat and electricity generation, further cutting emissions.

Explanation

Statement 1 is correct: Finely ground basalt rock is dispersed across agricultural lands to expedite the natural absorption of carbon dioxide from the atmosphere. This is known as enhanced rock weathering, where silicate minerals react with CO₂, forming stable carbonates and reducing atmospheric carbon, as well as improving the fertility of the soil.

Statement 2 is correct: This method, referred to as ocean alkalinity enhancement, encompasses the addition of lime (calcium oxide or calcium hydroxide) to the oceans to elevate their alkalinity. By doing so, it boosts the oceans’ ability to absorb and retain carbon dioxide from the atmosphere, thus assisting in carbon sequestration.

Statement 3 is correct: The process known as carbon capture and storage (CCS) involves capturing carbon dioxide emissions from industrial processes and storing them underground. Abandoned subterranean mines can be utilised as viable storage sites, where the captured carbon dioxide is injected into these locations as carbonated waters.

Explanation

An accelerometer is an electromechanical device used to measure acceleration forces. These forces may be static like the continuous force of gravity or dynamic force to sense movement or vibrations.

Statement 1 is correct: Upon a collision, the crash sensor, typically an accelerometer, transmits a signal to the airbag control unit to deploy the airbags almost immediately.

Statement 2 is correct: Accelerometers in laptops protect hard drives from damage. If the laptop were to suddenly drop while in use, the accelerometer would detect the sudden free fall and immediately turn off the hard drive to avoid hitting the reading heads into the hard drive platter.

Statement 3 is correct: Accelerometer is used in smartphones as it detects the rotation of their display between portrait and landscape mode depending on the tilt of the phone.

Explanation

Statement 1 is correct: The use of biofilters to remove toxins from wastewater and waste gases has advanced in recent decades. In order to remove contaminants from a fluid stream, biofilters fix microorganisms to an inorganic/organic medium (carrier), which has the ability to break down a wide range of chemicals. By removing uneaten fish feed, they additionally perform waste treatment.

Statement 2 is correct: By constructing a biofilter correctly, it is possible to regulate ammonia and nitrite concentrations at levels safe for fish. Through the biofiltration process, ammonia nitrogen is converted into nitrite nitrogen, which is subsequently transformed into less harmful nitrate nitrogen, ensuring a conducive environment for fish.

Statement 3 is incorrect: Biofilters do not increase phosphorus as a nutrient for fish in water. Phosphorus (P) is actually removed by biofilters to prevent eutrophication in waters.

Explanation

Green hydrogen is a renewable energy source that, unlike coal and oil, solely releases water vapour and leaves no residue in the air.

Statement 1 is correct: Hydrogen, a zero-carbon fuel, can be used to power automobiles through both hydrogen internal combustion engines and hydrogen fuel cells.Hydrogen engines utilize hydrogen in an internal combustion engine, operating similarly to the way gasoline powers conventional engines.

Statement 2 is correct: Clean hydrogen may be created and injected into natural gas pipelines to create blends that can be utilised to provide heat and power with fewer emissions than just natural gas.

Statement 3 is correct: A fuel cell harnesses the chemical energy of green hydrogen or alternative fuels to generate electricity in a clean and efficient manner. When hydrogen serves as the fuel, the sole byproducts produced are electricity, water, and heat.